Fun game and really well done :)
I like that you got different enemies (only had one in my game :P ) and I definitely feel lost jumping around your level. Would be nice to have a map, but maybe I just didn't find it? or its not in the demo? Also, haven't found the boss or air dash yet (did find the extra health tank though!), but I'm sure they're nice :P
The camera is a little wonky sometimes, the character sometimes end ups at the bottom or side of the screen instead of close to the centre. Also the character sliding to a stop made stopping on platforms challenging at first, but I got used to it.
Also, I liked the art and the opening "boss" encounter that forces you underground was exciting. Looking forward to playing more :)